湖南地区不同集约化栽培模式下双季稻稻田CH_4和N_2O的排放规律

CH_4 and N_2O emissions from double-rice field under different intensified cultivation patterns in Hunan Province

采用静态暗箱-气相色谱法研究了湖南双季稻稻田不施氮(NN)、当地常规(FP)、高产高效(YE)、再高产(HY)、再高效(HE)5种不同栽培模式下温室气体(CH4、N2O)的排放规律.结果表明:水稻生长季CH4累积排放量变化为(206.5±37.5)kg·hm-2(FP,早稻)～(490.5±65.7)kg·hm-2(HE,晚稻),N2O-N累积排放量变化为(0.08±0.05)kg·hm-2(NN,早稻)～(0.326±0.15)kg·hm-2(HY,晚稻).不同栽培模式对CH4和N2O的排放都有显著影响(p<0.05).HE模式CH4排放显著高于其他模式62%～87%(p<0.05),尤其是晚稻季节;除NN模式外,其他4种模式间N2O排放差异不显著.冬季休闲期也是CH4和N2O排放的重要时期,分别占全年排放量的9.7%～19.7%和42%～62%.CH4主导了稻田不同栽培模式下的综合温室效应,在各模式中均占95%以上.施氮肥提高了作物产量,降低了温室气体强度(GHGI).在5种模式中,YE和HY模式温室气体强度较小,HY模式下仅为(0.97±0.16)kg·kg-1(以每kg产量排放的CO2当量计).因此,与FP模式相比,YE和HY模式既能提高产量和氮肥利用率,也能减缓温室效应;但HE模式排放的温室气体较高,在实际应用前尚需进一步研究.

Methane （CH4） and nitrous oxide （N2O） from rice field in the double rice ecosystem in Hunan province were studied using static-chamber/gas chromatography. Five cultivation patterns or treatments were established including NN （no N as control）, FP （farmers′ practice）, YE （10%～15% higher in yield and 15%～20% higher in N use efficiency）, HY （30%～40% higher in yield）, and HE （20%～30% higher in yield and 30%～50% higher in N use efficiency）. The results showed that cumulative seasonal CH4 emissions ranged between （206.5±37.5） kg · hm-2 （FP, early rice） and （490.5±65.7） kg · hm-2 （HE, late rice） while cumulative seasonal N2O emissions ranged between （0.08±0.05） kg · hm-2 （NN, early rice） and （0.326±0.15） kg · hm-2 （HY, late rice）. During the rice growing season, CH4 and N2O emissions were significantly affected by different cultivation patterns （p0.05）. CH4 emissions under HE pattern increased significantly by 62%～87% during the late rice growing season. Except for NN, N2O emissions from the four fertilized patterns did not differ significantly among each other. The fallow period was a vital source of CH4 and N2O emissions which accounted for 9.7%～19.7% and 42%～62%, respectively, of the total annual emissions. Global warming potential （GWP） of CH4 emissions dominated the total GWPs under the double-rice ecosystem for all patterns, accounting for more than 95% of the total GWPs. The application of nitrogen fertilizer reduced greenhouse gas intensity （GHGI） significantly by increasing the rice yield. The YE and HY patterns produced lower GHGIs than other patterns, with only （0.97±0.16） kg（CO2-eq） · kg-1 of yield for the HY. Therefore, as compared to the FP, the YE and HY patterns should be promoted due to the increased rice yields and nutrient use efficiency and the reduced GHGI; while the HE pattern produced relatively higher GWP and GHGI thus deserving further research for greenhouse gas mitigations.